Friday, March 18, 2011

Epidendrum nocturnum, a night fragrant orchid native of Puerto Rico

This cleistogamous flower was opened to show the flower structure inside the unopened bud

See developing seed capsure at the lower right corner

Epidendrum nocturnum is an orchid with a very large geographical distribution. It can be found in Central America, the Greater Antilles and tropical South America. In Puerto Rico it is reported as growing in the coast as well as in the high peaks in moist areas in the east of the island. All the plants that I have seen have been in the middle to high points in the Sierra de Luquillo. There are three orchids in the Sierra de Luquillo that have very similar flowers, Epidendrum nocturnum, Epi. carpophorum and Epi. tridens. Epidendrumcapophorum is so distinctive in its vegetative form that it is easy to distinguish from the other two. Distinguishing between Epi. nocturnum and Epi. tridens it’s a bit harder but adult plants can be told apart because of the larger size of Epi. tridens.

In favorable habitats Epi. nocturnum is not rare, unfortunately I have yet to find a non cleistogamous plant. A cleistogamic plant is one that self fertilizes. In some cleistogamic species the flowers never open. This is the case of the Epi. nocturnum that I have found in the wild. There are several species of orchids in Puerto Rico that are self fertilizing. Why do plants do this? There is a theory that says that cleistogamy allows plants to colonize areas where their natural pollinators are not present. There are a number of species of Puertorican orchids that are pollinated in the continents by insects that are not present in the island. A good example is the genus Dichaea, in those areas of South America where they grow they are pollinated by Euglossine bees, these bees are absent from Puerto Rico and yet local Dicheas reproduce well enough without them. In these species cleistogamy is suspected even in those cases where the flowers open fully.

I have seen this plant growing in boulders in the middle of streams and in the trunk of tree ferns and Sierra Palms. One interesting detail is that the healthiest plants all were growing in areas where there was an opening in the canopy. These openings in the canopy could be in the middle of a river, in an area where a landslide or tree fall allowed the sunshine to penetrate into the forest and in the areas bordering roads. This tells me that this plant grows best if it received bright light which may include being exposed to full sun for some time during the day.

The presence of seedlings growing under the cleistogamic plants show that this strategy is fairly successful locally. This plant has a delightful perfume that is produced at night. This plant is grown horticultural but all the plants I have seen in cultivation have been produced commercially outside Puerto Rico. I was pleasantly surprised to see seedlings of this species for sale in the 2011 Puerto Rico Orchid Society annual orchid show. The easy availability of plants produced in captivity, and the general absence of this species from most orchid collections probably means that wild collection of this species in Puerto Rico is apparently very rare. I have yet to see plants of this species exhibited at orchid shows, the reason is not clear but it may reflect a preference for showing flowers with larger and more brightly colored flowers rather than any particular rarity of the species in captivity.

You can easily see the massive root system of this plant

I recommend this orchid for those people that place a great value in the fragrance in orchids. I have not cultivated this plant but from observations of its habitat I would think this plant needs regular watering, high enviromental humidity and bright light to do well. In all cases where I have seen this plant growing the roots were exposed to the air which indicates that this is a plant that needs an open, airy media to do well if grown in a pot. Another alternative is to grow it mounted on a slab or plaque. The downside of growing this it mounted is the need for copious watering during the peak of the dry season to avoid the death of the plant from dehydration.